There are some physiological changes that you simply cannot avoid as you age. That said many ride on in ignorance. Different things become important to the aging cyclist. If you have not read this I highly recommend it:

http://www.amazon.com/Pruitts-Comple.../dp/1931382808

In addition it is unlikely that one has reached a significant age as a competitive athlete without sustaining injury. Those injuries have a greater cumulative effect as we get older. Getting a true medical bike fit and custom bike goes a long way (assuming you can withstand the major dent in your pocketbook). Riding comfort can easily equate to improved power output and performance. The young that lack coaches typically are far less knowledgeable than the aging peloton which is why they are so often dusted by riders twice their age.

Take advantage of the things that usually go hand in hand with older age - experience, financial resources (coaching, equipment and the occasional Pinot Noir!), time to train (the retired guys can be insane due to the significant time they have available). All in all it looks quite favorable.